Index in position 1 is invalid. Array indices must be positive integers or logical values. My Events

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Matt Egan 2020-4-12

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/517306-index-in-position-1-is-invalid-array-indices-must-be-positive-integers-or-logical-values-my-events

评论： Ameer Hamza 2020-4-12

I am currently working on an inverted pendulum problem. I have used the My event funtion to stop the penduum action at 45degree (please see code and function below). The highlighted line is causing problems. It is my understanding this is the strating conditions of the pendulum, but if i set to [0,0] it comes up with the above error. The current conditions are not correct but i am unable to change them and run the programme.

function zdot=crash(t,z,g,r,m,k,a)
zdot=zeros(2,1);
zdot(1)=z(2);
zdot(2)=(r^2*z(2)^2-r*a*cos(z(1))-r*g*sin(z(1)))/(k^2-2*r^2);
end
function [value,isterminal,direction] = dashboard(t,z)
  minz = (pi/4);   %for example
  value = z(:,1) < minz; 
  isterminal = 1; %stops the integration
  direction = 0; % The zero can be approached from either direction, -1 decreasing function, +1 increasing fucniton
end
clear;clc
%crash conditions
g=9.81; r=0.4; k=0.5; m=40; a=98.1; 
 
tspan1=(0:0.002:5);
z0=[pi/2 0];
 
z0=[0, (a/r)^0.5];  <<<<<<<<<<<<<<<<<<<<----------------------------------------THIS LINE
Opt    = odeset('Events', @dashboard);
[t,z]=ode45(@(t,z)crash(t,z,g,r,k,a,m),tspan1,z0,Opt);
 
ind = interp1(z(:,1),1:length(z(:,1)),pi/4,'nearest');
 
V_g=z(ind,2)*r
 
V_h=z(ind,2)*.75